1. Field
One or more example embodiments relate to a microwave filter system having a feedback structure, and more particularly, to a microwave filter having a feedback structure that may decrease an input/output reflection loss and achieve not an insertion loss but a gain.
2. Description of Related Art
With the development in Internet technology (IT), frequency resources of a low frequency band used for the industrial purpose is being depleted. To solve the above issue, researches are currently conducted to use a broad frequency band ranging from a few to tens of gigahertz (GHz), such as microwave and millimeter wave bands.
In particular, a frequency filter is an important part used to selectively receive and transmit a signal of a specific frequency band, and requires an excellent selectivity and input/output matching characteristic. To meet the requirements, a high-order filter is to be configured by applying a plurality of integrated chips (ICs) on a substrate. However, the high-order filter may not be readily configured due to some difficulties coming from characteristics of the substrate and the ICs.
In the related art, researches on a microwave filter including a feedback circuit using two power dividers haven conducted. However, since a power divider does not include an isolated port, the leakage of a signal may occur. Accordingly, a signal distortion may occur or a group delay characteristic may be degraded in the microwave filter according to the related art. Also, in the microwave filter, overlapping may occur between a signal input to the feedback circuit and an original signal. Accordingly, a signal distortion may occur.